A common greeting in reference to someone who looks like Paul 'Bonehead' Arthurs the rhythm guitarist (sometimes celloist) of Oasis. Bonehead himself maybe recognised for having a casual look on his face constantly and having soft cheeks, like that of a peach. the word 'Cha' is a bastardization of 'Here' which is nowadays used frequently in Geordie Slang
"Cha Bonehead" *slaps head*
"Cha Boneheadaaaaaaaa stop molestin meeeaaa"